Streptococcus mutans has been implicated as a major causative agent of dental caries. Interference with this organism should markedly reduce human caries. Ribosomal vaccines against S. mutans have been used previously by other investigators but these ribosomal preparations usually contain cell wall- and membrane-associated antigens and other antigens of undefined nature which may cross-react with human tissues. It appears that one of the major questions to be answered is that whether ribosomes and not the contaminants are useful vaccines in the protection against dental caries. If ribosomes are indeed useful vaccines, its mechanism of action should be unique and warrents further investigation. Accordingly, the specific aims of the present proposal are to prepare robosomes from S. mutans of the highest degree of purity to exclude nonribosomal contaminants. The purity of the ribosome will be monitored by biochemical assays to assess the amount of protein, RNA, DNA and carbohydrate. The sedimentation values of these purified ribosomes and their subnits will be determined by sucrose density gradient centrifugation. The protein and RNA composition of these highly purified ribosomes will be examined by polycrylamide gel electrophoresis. Such highly purified ribosomes will be used as immunogens to raise antibodies in rabbits. The specificity of these antibodies will be tested against homologous S. mutans ribosomes and whole cells as well as components of other serotypes using Ouchterlony diffusion procedure and the Western blotting procedure. In addition, specific RNA-protein complexes will be construced from purified ribosomal RNA and proteins. Such complexes will be used as antigens. The antibodies will also be tested for their effectiveness against S. mutans. The rationale for using reconstituted ribonucleoprotein complexes is that the chemical nature of the immunogen is defined and should not contain any non-ribosomal contaminants. The specific RNA-protein complexes will consist of 5S RNA and proteins from the purified large ribosomal subunit of S. mutans. The identity of the proteins in the complex will also be determined by 2-D polyacrylamide gel electrophoresis. If time permits during this funding period, these highly purified ribosomes or RNA-protein complexes will be administrated to animals and the salivary and serum immune responses will be studied in order to test the potentials of using these defined antigens as caries vaccines.